I am transferring from Max to Maya , so i have a problem with Moving key frames in the time line over other key frames , in Max when you drag a key frame over another one it will override the old one and keep only the new key , but in Maya it keeps both keyframes with a tinny gab between them , witch makes a lot of unexpected result in animation and a hard time finding this keys and delete them , is there any option in Maya that i can check to make life easier for me?....

By tiny gap, do you mean that the keys are located on fractions of frames? Like a key sits on 3.723 time? If so, in the timeline settings there's an option to turn on discrete frames (can't remember what it's exactly called) so that keys can only sit on integer times; then you shouldn't have keys separated by tiny gaps and it's easier to see where the keys are. Also, try opening the graph editor and see if that helps you.